NAD 1700 - FM Alignment Procedures - Part 2; Detector Alignment; Stereo Separation and Distortion; Auto Search and Switching Levels

. DETECTOR ALIGNMENT
. Remove Detector Probe, and connect the Tape, Output to Distortion Analyzer and Oscilloscope.
. Connect DMM between TP-103 (—) and TP-104 (4).
. Tune to 98MHz and feed 1000uV from FM Generator (Modulate 1kHz 100%, Mono).
. Adjust L-102 Secondary for lowest THD. Specification: less than 0.12%.
. Adjust L-102 Primary for OV reading on DMM. Tolerance: +/— 50mV.
. Repeat above steps 4 & 5 until no further improvement.
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. STEREO DISTORTION & SEPARATION
. Tune to 98MHz and feed 1000uV from FM Generator. Modulate 1kHz, 100% left (or right) only.
. Adjust L-101 and L-8 just slightly so that distortion on left (or right) channel becomes minimum.
. Check stereo distortion, wide IF: Specification: less than 0.1%, L + R, L only, R only, L — R.
. Next, select IF NARROW, and check distortion: Specification: less than 0.15%, L only, R only, L— R.
. Set IF to wide and modulate L only. Adjust R-375 for minimum output on right channel.
Next, modulate R only and adjust R-375 for minimum output on left channel.
lf necessary, readjust R-375 so that readings become same on both channels. Specification: more than 46cB.
6. Select IF NARROW, and modulate left (or right) channel only. Adjust R-376 for minimum output on right
(or left) channel VTVM and Oscilloscope.
If necessary, readjust R-376 so that readings become same on both channels. Specification: more than 40aB.
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. AUTO SEARCH LEVEL
1. Set IF to wide. Connect DMM between TP-105 and Ground:”
2. Set FM Generator output to 10uV and adjust R- o78 so cent reading just goes from OV to 40V.
Tolerance: +/— 2pV.
. STEREO SWITCHING LEVEL
1. Set FM Generator output to 5uV, 1kHz 100% L + R.
2. Adjust R-379 so that the stereo
light just turns on. Tolerance: + 2uV.
Note: The tuner will switch into mono at a lower level, ‘ypically 4uV.
. SIGNAL METER LEVEL
1. Tune to 98MHz and feed 100uV from FM Getic ator
2. Adjust R-380 so that fifth LED just lights.
PARTIAL MUTING
1. Set FM Generator output to 0.5uV, 1kHz 30% Mono modulation. Set R-381 full CCW.
2. If S/N above 702760; set FM NR on, tune away from, then back to, RF Generator frequency.
3. Adjust R-381 so that muting just turns off.
. FM NR CIRCUIT: MULTIPLEX FILTERS
1. Check that FM NR is off.
. Set FM Generator output to 2000uV, 1kHz 100% L + R, and set reference for S/N measurement. Cancel the
stereo modulation and leave pilot tone.
. Adjust FL 102 (FL 103) for minimum subcarrier output on left (right) channel; Specification: less than — 60dcB:
. Adjust FM Generator output so that S/N ratio reads 50cB.
. Switch FM NR on, and adjust R-148 so the S/N is improved by 8dB.
. Switch FM NR off, and adjust FM Generator output so that S/N ratio reads 60cB.
. Switch FM NR on, and check that S/N is improved by approx. 2dB.
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